The roly-poly or pill bug (Armadillidium vulgare) is a crustacean, not a bug, although its many names might mislead you. In addition to the two names above, they are also called woodlice, tiggy-hogs, armadillo bugs, potato bugs, and parson-pigs. Contrary to their odd monikers, they are not lice, pigs, or armadillos and they don’t eat potatoes. You may also find alternative spellings: rolly polly and rollie pollie and variations thereof are common as well as pillbug as all one word. While these spelling differences may seem inconsequential, they can help you when searching for information on these little crustaceans. We will primarily refer to them as roly-polies throughout this article.
Roly-polies are small gray crustaceans (the same taxon as crabs, shrimp, and lobsters) with exoskeletons composed of seven overlapping plates. They are nocturnal and typically found beneath leaf matter, rocks, and fallen logs. They are called roly-polies because they roll themselves up into a ball when they feel threatened. This is also where one of their other names comes from: a rolled-up A. vulgare resembles a pill.
Since they can’t bite or sting, this is their primary defense mechanism, which they supplement with an unpleasant odor.
Their bodies are segmented into three primary parts – the head, the thorax, and the abdomen – and they have fourteen legs arranged in pairs (two per plate). They also have eyes and antennae and though they possess gills like the marine members of their taxon, they cannot survive underwater. However, they do require moisture for survival. They and the closely related sowbugs (together comprising about 5,000 species) are the only crustaceans that live entirely on land. Though they look similar, roly-polies are distinguished by their ability to roll up into a ball, which sowbugs do not possess.
Roly-polies hatch from eggs and live for between 1.5 and 5 years, undergoing up to twelve different molt cycles in a lifetime. Females produce as many as 3 broods of up to 50 eggs each per year. She carries these eggs in a pouch (called a marsupium) on the underside of her body. They hatch in about 2 months. Even after hatching, baby roly-polies live inside the pouch for several days.
The focus of this article is the roly-poly diet. Perhaps you found some of the little guys hanging out under a plank of wood in your garden and you’re worried they might damage your plants. Maybe you’re wondering, “What do roly-poly bugs eat?” Or perhaps, “What do rolly pollies eat?” Or maybe even, “What do rollie pollies eat?” Whichever way you spell their name, we’ll tell you all about their diet.
Roly-polies serve a primary decomposition role in their ecosystems, feeding on the organic matter of deceased plants, fungi, and animals as well as fecal matter (including their own). Roly-polies increase important nutrients in the soil through the breakdown of organic matter.
They further increase soil pH and remove significant quantities of carbon from dead leaves. They consume heavy metals, such as copper, zinc, arsenic, cadmium, and lead, removing them from the soil. This makes them highly resistant to contaminated soils in which other critters can’t survive.
This propensity for eating metal is also why they eat their own feces. Their waste-producing process isn’t perfectly efficient and they lose some crucial copper during defecation, so they eat their poop to replenish their copper stores. By decomposing organic matter and injecting nutrients into the soil, they improve soil conditions for plant growth. This makes them a very important part of the ecosystems in which they live.
So, do rolly pollies eat plants? Yes. They do sometimes feed on living plants and even animals. This includes roots, seeds, and plant seedlings as well as stink bug eggs and other roly-polies. Stink bugs are major garden and crop pests, making roly-polies desirable for pest control. Alternative feeding typically only occurs when their populations grow too large for the existing supply of dead and decaying matter. While young plant growth is the most common alternative diet item for roly-polies, they also consume leftover fruit that insects don’t finish.
Damage to plants
Though they are typically beneficial to have in the garden, they have been known to cause some crop damage. Specifically, they feed on the leaves and roots of tomatoes, carrots, radishes, lettuce, peas, beans, cucumbers, mustard, and fruit. Furthermore, when they eat seeds, they necessarily prevent the growth of some plants. While large populations can cause losses in gardens and greenhouses, significant damage is rare and roly-polies are not commonly considered pests.
Roly-polies are funny-looking land-dwelling crustaceans that serve a crucial role in their ecosystems. Here, we’ve covered their major diet items as well as what they eat when their preferred food resource is scarce. While they do eat live plants and have the potential to damage garden plants, it’s rare that they cause enough damage to be considered pests. They do more good than harm. So, if you came here wondering, “What do pill bugs eat?”, we hope we’ve satisfactorily answered your question.